BackgroundWolffian adnexal tumor is a rare type of tumor that was first discovered and reported by Karim‐inejad in 1973. Wolffian adnexal tumor lacks specific clinical manifestations and its histological morphology is similar to various other tumors, making it highly prone to misdiagnosis. To enhance our understanding of this disease, we hereby report a case of Wolffian adnexal tumor diagnosed and treated in our hospital.CaseIt is the first report of a giant bilateral Wolffian tumor, with pleural effusion and pericardial effusion as the initial symptoms. Magnetic resonance imaging (MRI) suggested a huge lobulated mass (25.3 × 17.8 × 21.9 cm) in the mid‐lower abdomen and pelvis, involving both ovaries. A diagnosis of “ovarian malignancy” was made before the surgery. Hysterectomy, bilateral adnexectomy, and omentectomy were performed. Postoperative pathology revealed a bilateral Wolffian tumor. Postoperative chemotherapy with a taxol and cisplatin (TP) regimen was administered for six cycles. Follow‐up at 2 months postoperatively showed resolution of pericardial and pleural effusions, and there has been no recurrence during the 3‐year follow‐up period.ConclusionWolffian adnexal tumor lacks specific clinical manifestations, and its prognosis is good after treatment.